Bus impedance matrix based approach for congestion management in deregulated environment

This paper addresses the problem of congestion management in deregulated environment by utilizing bus impedance matrix. The use of bus impedance matrix is explored to determine the sensitivities of line flows in congested transmission lines as a function of bus injections. A congestion management optimization problem is formulated to minimize the cost involved in re-dispatching the generators based on incremental and decremental bids subject to line flows (as determined from bus impedance matrix based sensitivities) congestion constraints and bounds on rescheduled power generations. The benefit of this approach is that in contrast to conventional load flow jacobian matrix based sensitivities, the bus impedance matrix based sensitivities are independent of the selection of slack bus; therefore it guarantees a fair rescheduling of generators and allocation of congestion cost in deregulated environment. The effectiveness of proposed methodology is proved with case studies on a 4-bus and IEEE 30-bus system and results obtained are compared with that of conventional jacobian matrix based approach.